Ensure the right content is served for the build artifacts API

spec/requests/api/builds_spec.rb

@@ -188,6 +188,7 @@
         it 'returns specific build artifacts' do
           expect(response).to have_http_status(200)
           expect(response.headers).to include(download_headers)
+          expect(response.body).to match_file(build.artifacts_file.file.file)
         end
       end
 

spec/support/matchers/match_file.rb

+RSpec::Matchers.define :match_file do |expected|
+  match do |actual|
+    expect(Digest::MD5.hexdigest(actual)).to eq(Digest::MD5.hexdigest(File.read(expected)))
+  end
+end